The SRG/eROSITA All-Sky Survey: A comprehensive X-ray analysis of the Hydra I galaxy cluster

Abstract

The Hydra I galaxy cluster (Abell 1060) is a nearby example of a low-temperature cluster that exhibits intermediate cool core and non-cool core properties. Our aims are to extend the characterization of the intracluster medium (ICM) properties at least until $R_{200}$ and study the correlation between the X-ray emission and non-thermal emission within $R=0.15$$R_{500}$, and optical/IR galaxy distribution beyond $R_{200}$. We used data from the first four SRG/eROSITA All-Sky Surveys and an archival Chandra observation to image the X-ray emission from Abell 1060. We also used multiwavelength data from TGSS (radio), 2MASS (IR), and NED (optical) to investigate the non-thermal emission, 2D galaxy distribution, and its redshift evolution, respectively. The surface brightness and spectral analyses are also extended until 3$R_{200}$ and $R_{200}$, respectively, following a detailed cosmic X-ray background (CXB) analysis. Our fully corrected eROSITA image showcases a relaxed ICM morphology within $R_{500}$. We detected two surface brightness discontinuities near the central galaxy NGC~3311 that spatially coincide with diffuse radio emission along the line of sight. Furthermore, we detected two soft X-ray excesses with high spatial correlation with the 2D optical galaxy distribution beyond $R_{200}$. In particular, the excess in the north has a significance of $3.9σ$ above the local CXB level. This suggests that Abell 1060's outskirts are actively accreting baryons. We also estimated the average ICM temperature and metallicity of $\langle k_\mathrm{B}T \rangle=2.51\substack{+0.21\\-0.21}\thinspace$ keV and $\langle Z\rangle=0.19\substack{+0.10\\-0.10}\thinspace Z_\odot$, respectively, from the 0.2-0.5$R_{500}$ annulus. Overall, the temperature profile is broadly consistent with the average temperature profiles from hydrodynamical simulation and Suzaku between 0.43$R_{500}$ and $R_{500}$.